1. Field of the Invention
The present invention relates generally to an apparatus and method for conserving power in a computer controlled system. The present invention relates more specifically to conserving power in an apparatus containing a positioning mechanism.
2. Related Art
In servo motor control systems, a motor is controlled by applying a voltage reference signal representing a desired motor position to a motor driver which provides current to the motor. The motor responds to the current by turning a motor shaft. A motor encoder attached to the motor shaft senses the position of the motor shaft as it turns. A motor encoder signal representing the actual motor position is fed back and compared to the desired motor position. The difference between the desired motor position and the motor encoder position is used to compute the voltage reference signal which is then applied to the motor drivers. In theory, this process continues until the difference between the desired motor position and the motor encoder position is zero, or in other words, until the desired motor position and the actual motor position are the same.
A problem with this process in actual practice is that once the motor reaches the desired motor position, some voltage level must be continually applied to the motor drivers to overcome external forces such as gravity to maintain the position of the motor. Significant heat builds up within the motor and the motor drivers when the servo motor control loop is required to maintain the position of the motor for a long period of time. This build-up of heat results in decreased reliability of the motor electronics especially in applications where the motor is used to position a substantial mass such as a robotic arm of an optical autochanger.